Traditional detergents used in laundry are typically formulated at a high pH (i.e., above 7), because high pH enables the use of traditional builders and surfactants. However, it has been found that certain acidic detergents (i.e., with pH below 7) may provide benefits such as improved removal of residues from fabrics and associated improvement in whiteness, improved bleachable stain removal, and self-preservation benefits.
It is desirable to both the formulator and the consumer that such detergents have desirable viscosities. Compositions with viscosities that are too high may be difficult to process or to use; viscosities that are too low may indicate a lack of cleaning power or value to the consumer. In order to obtain desirable viscosities, many detergents, especially those that have high levels of water (e.g., above 60%), require the use of thickening agents. For example, a formulator may add salt, such as sodium chloride or sodium formate, to thicken compositions that have low viscosities.
However, such thickening agents can present difficulties. For example, certain thickening agents, such as salt, may have corrosive effects at low pH on metals commonly used in manufacturing plants, such as 316 stainless steel. Thickening agents may lead to stability challenges such as “salting out.” There may be limits to the amount of viscosity that can be built with thickening agents. And, of course, the use of thickening agents adds extra cost to a composition.
Therefore, there is a need for an effective, low cost solution to thickening high water, low pH detergent compositions. It has been surprisingly discovered that blending high HLB and low HLB nonionic surfactants in high water, low pH detergent compositions can yield compositions with desirable viscosities without the use of thickening agents.